It wouldn???t surprise me that your cake was dense when using baking POWDER, rather than the SODA called for; baking POWDER is only 1/4 as powerful as the equivalent baking SODA. I wouldn???t expect it to affect dryness, however, other than the fact that your cake wouldn???t have browned as easily with the POWDER and you???d have had to leave it in the oven longer if you were gauging the doneness